The primary function of industrial fans is to provide a large fluid flow, with general utility in/for processes such as combustion, ventilation, aeration, particulate transport, exhaust, cooling, air-cleaning and drying. Fluid flow deliver is accomplished by rotating a number of blades, connected to a hub and shaft, and driven by a motor or turbine. Industrial fans are generally categorized as being either centrifugal or axial in nature, with each having a characteristic fluid flow path indicative of their monikers.
Centrifugal fans use a rotating impeller to increase the velocity of a fluid. As the fluid moves from the impeller hub to the fan blade tips, it gains kinetic energy, which in turn is converted to a static pressure increase as the air slows in advance of discharge.
Axial fans move fluid along the axis of the fan. The fluid is pressurized by the aerodynamic lift, i.e., axial forces, generated by the fan blades. Propeller, tubeaxial and vane axial fans are well know variants of this style fan, with the tubeaxial and vane axial being more complex versions of the propeller fan.
As is well known and documented, disruptions in connection to fluid flow fan ingress/egress can be particularly problematic, with at least one of either inlet or outlet flow conditioning proving advantageous, and, on occasion, both. For example, rotational energy can be translated into useful energy by a guide vane arrangement on an inlet, or more often times, on an outlet side of an axial fan. With such arrangement, a rotational velocity flow component is converted to an axial velocity component, with pressure correspondingly raised, and thus fan efficiency improved.
Guide vanes, in the form of airfoil structures, are known for conditioning unidirectional fan discharges (see e.g., U.S. Pat. No. 7,730,714 (Wood et al.) and U.S.Pub. U.S. 2012/0128494 (Pelley et al.)). Uniformly configured guide vanes in the form of single thickness elements are also known (see e.g., U.S. Pat. No. 5,246,339 (Bengtsson et al.) & U.S. Pat. No. 5,180,106 (Handfield)) as well as those part-and-parcel of a flow control device in the context of serial axial fans used in/for cooling electronic devices and the like (see e.g., U.S. Pat. No. 6,508,621 (Zeighami et al.), U.S. Pat. No. 7,942,627 (Jin), & U.S.Pub. U.S. 2008/0138201 (Lin et al.)). Moreover, non-uniformly configured guide vanes (FIG. 3E) and non-uniformly arranged (i.e., non-homogeneous) guide vanes (FIGS. 3C & D), provided in the form of a flow conditioning ring, are likewise known, at least in the context of lowering tonal components associated with fan operation (U.S. Pat. No. 5,470,200 (Tupov et al.)).
In a bidirectional context, axial fans are likewise known to include vanes for condition the flow passing through the impeller (see e.g., U.S. Pat. No. 4,219,325 (Gutzwiller) & U.S. Pat. No. 6,508,622 (Neumeier)). As to the former, in lieu of adjustable vanes and adjustable impeller blades, first and second sets of concavo-convex vanes, disposed adjacent each side of the impeller, are provided for in the context of a plug unit for a heat treating furnace (FIGS. 1 & 2), the arrangement generally being symmetrical (i.e., a 90° rotation of the FIG. 1 view provides an identical vane arrangement). As to the latter, a rotatable inlet stator 15 having a guide vane 17, and a rotatable outlet stator 16 having a guide vane 18 which is mirror-symmetrical to vane 17 (FIG. 2), the rotor disposed therebetween, is generally provided in the context of tunnel ventilation. Further contemplated are inlet and outlet vanes which are characterized by a fixed position section 22 and an adjustable section 23. Essentially, in reverse flow operation, the structures are adjusted such that the inlet stator 15 takes on the function of a downstream stator and downstream stator 16 takes on the function of an inlet stator.
While particularized fluid flow efficiency solutions are set forth with regard to inline fans, both in the context of unidirectional and bidirectional flow, solutions as to the latter are believed overly cumbersome. Notionally, competing interests or objectives are present with regard to inline fan systems, namely, there exists a design tension between aerodynamic load and structural load. While aiming to reduce, among other things, material quantities, the number of parts, and geometric complexity while nonetheless at least retaining, if not improving upon aerodynamic performance and mechanical stiffness, a less-is-more approach is believed advantageous. Provisions for an improved, low cost, low complexity guide vane which generally enhances fan/fan system performance with regard to fluid flow in a first or primary direction, yet nonetheless maintains at least a suitable fan/fan system performance in a second/secondary reverse flow is believed advantageous and heretofore unknown.